1. Field of the Invention
The present invention relates to the field of spark generation in internal combustion engines and, more specifically, to a novel spark plug with a ground collar, firing ring, and capped central electrode which are made of a novel alloy to produce multiple, simultaneous, sparks from multiple locations around the periphery of the cap.
2. Art Background
In internal combustion engines, the spark plug serves as the spark-generation source which fires at pre-determined intervals in order to ignite the air-fuel mixture within a given cylinder of the engine. Spark plugs of conventional design typically comprise a concentric arrangement of three structural elements: (1) a central electrode; (2) an insulator, such as a ceramic jacket, that surrounds the periphery of the central electrode; and (3) an outer shell, including an outer ground electrode, that surrounds the periphery of the insulator.
The central electrode is in the shape of a solid cylindrical pin, with proximal and distal ends that project axially from either end of the spark plug. In addition, a portion of the outer shell is threaded, wherein the threaded portion mates with a corresponding threaded portion in the engine head above the cylinder to create a tight fit between the engine head and the spark plug. Once the spark plug has been threaded into position in this manner, the proximal end of the central electrode projects axially out of the spark plug body and into the cylinder, while the distal end projects out of the spark plug and in a direction opposite the proximal end.
In operation, the central electrode is adapted to receive an electrical charge at its distal end, which charge is then conducted forward to the proximal end of the electrode, inside the cylinder. Given the construction of the spark plug, an electrical gap exists between the proximal end of the central electrode, on the one hand, and the proximal end of the ground electrode, on the other. As such, the electrical charge that is applied to the distal end of the central electrode must be sufficiently large to xe2x80x9cjumpxe2x80x9d the gap and create a spark at the appropriate moment in time (e.g., during the latter portion of the compression cycle of the piston within the cylinder). The spark generated then ignites the pressurized air-fuel mixture within the cylinder which, in turn, causes the piston to repel, thus producing mechanical energy.
As can be seen from the brief description presented above, the performance of a given engine depends, to a great extent, on the structure, material composition, and proper operation of the spark plug. For example, depending on the materials used to manufacture the central and ground electrodes, the spark plug may be more prone to fouling (i.e., build-up of Carbon) than is desirable. Fouling, in turn, adversely affects not only the longevity and operation of the spark plug, but also the efficiency of the engine. In addition, considering the range of high operating temperatures in a typical engine cylinder (e.g., 900xc2x0 F. to 2200xc2x0 F.), the material make-up of the spark plug determines the type of engine in which a given spark plug may be used without running the risk of compromising its structural integrity.
The materials used also affect the useful life of the plug for that engine. Moreover, it has been determined that spark generation across a gap is achieved more easily from sharp edges and/or tips on the proximal end of the central electrode. In this regard, the material composition of the central electrode determines the speed with which wear (i.e., rounding of edges) occurs in a given spark plug. Depending on the extent of wear on an electrode, the spark plug may misfire (i.e., be delayed in firing), which will directly affect engine efficiency and emissions.
As was mentioned previously, in order for an engine to operate properly and efficiently, the plug must produce a spark during a time window towards the end of the compression stroke of the piston within the engine cylinder. If the spark is generated at a point that is outside of this time window, combustion will take place either prematurely or too late. As a consequence, the fuel-air mixture will burn only partially, which will adversely affect not only fuel efficiency, but also power generation and the production, retention, and release of harmful emissions. As such, it is imperative that the spark plug fire in a manner that is temporally synchronous with the cyclical operation of the engine cylinder. In addition, the more (spatially) uniform the spark generation, the more efficient and complete the combustion within the cylinder.
Attempts have been made to address some of the concerns mentioned above by, e.g., attaching an enlarged tip, or cap, to the proximal end of the central electrode (see, e.g., U.S. Pat. Nos. 5,767,613 and 5,731,655), attaching an L-shaped, or other similar extension, to the ground electrode to provide various gap sizes and geometries (see, e.g., U.S. Pat. Nos. 5,280,214 and 5,821,676), attaching annular rings, or cylindrical extensions having holes through the wall thereof, to the spark plug outer shell (see, e.g., U.S. Pat. Nos. 3,958,144 and 5,623,179), and employing metal alloys including Nickel and/or Platinum in the composition of the electrode material in an attempt to increase the useful life of the spark plug (see, e.g., U.S. Pat. No. 5,107,168).
However, there is still a need for a spark plug that offers structural integrity and longevity while, at the same time, providing for increased engine efficiency and reduced emissions as byproducts of the combustion process. This invention satisfies these and other needs.